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Space Exploration is the
science and engineering of spacecraft and space probes used for
investigation of physical conditions in space and in celestial
bodies - e.g. stars, planets and their moons. Space exploration, or
astronautics, is interdisciplinary in that it draws upon the
findings of such fields as physics, astronomy, mathematics,
chemistry, biology, medicine, electronics, and meteorology.
Automated space probes and human spaceflight have
provided a wealth of scientific data on the nature and origin of
the solar system and the universe. Although studies from earth
using optical and radio telescopes had accumulated much data on the
nature of celestial bodies, it was not until after World War II
that the development of powerful rockets made direct space
exploration a technological possibility.
Imagined for centuries, the era began with the
first artificial satellite (Sputnik, 1957) and the first manned
flight (Gagarin, 1961), with subsequent rapidly evolving
capabilities in Earth orbit and Solar System exploration (initiated
by Mariner 2, 1962). It is an arena of intense international
competition and, recently, co-operation. The utilitarian uses of
space - communications and meteorology - are now taken for granted;
astronomy and Earth remote-sensing capabilities provide a new
perspective on the universe and our own planet.
Solar System exploration has provided
reconnaissance as far as Neptune, in-depth exploration of Mars and
Venus, and detailed study of the Moon; the study of comets and
asteroids is less advanced. Human activity has been demonstrated
even to the point of crewed lunar landings (Apollo programme,
1969-72) and continuing space station occupancy (Salyut and Mir
space stations), but remains dangerous and costly.
Launch vehicle advances have achieved a re-usable
crewed orbiter (US space shuttle), but inexpensive, reliable
transportation is still in the future. The two dominant
participants have been the USA and USSR (now Russia), with the
Europeans and Japanese becoming increasingly influential. Space
physiological effects on humans are likely to limit the rate at
which future exploration proceeds.
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The father of modern rocket propulsion is the
American physicist, Robert Hutchings Goddard. Along with Konstantin
Eduordovich Tsiolkovsky of Russia and Hermann Oberth of Germany,
Goddard envisioned the exploration of space. During World War I
(1914-1918) he began experimenting with rockets. By 1918 he had
improved rocket design by using smokeless powder instead of black
powder and by adding a nozzle that improved the rocket motor's
efficiency. In memory of this brilliant scientist, a major space
science laboratory, NASA's Goddard Space Flight Center, Greenbelt,
Maryland, was established on May 1, 1959.
Rocket engines are reaction engines. The basic
principle driving a rocket engine is the famous Newtonian principle
that "to every action there is an equal and opposite reaction". A
rocket engine expels mass in one direction and moves with the
reaction that occurs in the other direction as a result.
A rocket is propelled by the expulsion of gases
generated in a combustion chamber. A rocket develops thrust
independent of its surroundings, unlike jet engines that need
oxygen from the atmosphere to burn fuel. A rocket engine is
self-contained and is currently the only type of device suitable
for space flight.
Rockets may be divided into two classes:
solid-propellant rockets and liquid- propellant rockets. In both
types the combustion chamber is called the motor. In a liquid-
propellant rocket, the propellants are carried in separate tanks
and transferred to the rocket motor; in solid-propellant rockets,
the propellant charge is stored and burned in the motor.
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Elementary, my dear
Goddard... As a method of sending a missile
to the higher, and even to the highest parts of the earth's
atmospheric envelope, Professor Goddard's rocket is a practicable
and therefore promising device. It is when one considers the
multiple-charge rocket as a traveler to the moon that one begins to
doubt ... for after the rocket quits our air and really starts on
its journey, its flight would be neither accelerated nor maintained
by the explosion of the charges it then might have left. Professor
Goddard, with his "chair" in Clark College and countenancing of the
Smithsonian Institution, does not know the relation of action to
re-action, and of the need to have something better than a vacuum
against which to react ... Of course he only seems to lack the
knowledge ladled out daily in high schools. -- New York Times Editorial,
1920
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The space age began on October 4th, 1957, when
the USSR launched Sputnik 1, the world's first artificial
satellite. One month later on November 3rd, Sputnik 2 was launched
carrying Laika, a black and white dog. Explorer 1 was launched by
the U.S. in January 1958. In October 1958 the National Aeronautics
and Space Administration (NASA) was created in the U.S.
Earth-orbiting satellites have improved global
communications, weather forecasting, navigational aids, and
reconnaissance of the earth's surface for the location of mineral
resources and for military purposes.
Hundreds of communications satellites reflect or
relay radio signals, providing transmission of television signals,
telephone conversations, and digital data. Weather satellites
provide daily reports of temperatures and cloud patterns. The U.S.
Landsats observe the earth, returning information on soil
characteristics, water and ice quantities, pollution, insect
blights of crops, and even forest fires. Study of the earth's crust
helps geologists to identify deposits of oil and minerals.
Navigation satellites can locate a position on earth within a few
yards. See lower down for Astronomy from Space.
The first space flight by a human was on April
12th, 1961. Yuri Gagarin, a Soviet cosmonaut, orbited Earth once in
the Vostok 1 spacecraft. Manned spaceflight started with suborbital
and orbital flights by a single astronaut (USA: Mercury) or
cosmonaut (USSR: Vostock); subsequent flights include
- the
launching of several crew members in a single capsule (beginning
with Gemini and Voskhod),
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rendezvous and docking of two spacecraft (beginning with Gemini and
performed internationally in the Apollo-Soyuz Test Program),
- lunar
orbit and landing (Apollo),
- the
launching of space stations (Salyut, Skylab, and Mir),
- and the
launching of a reusable space vehicle, the space shuttle.
On July 20th, 1969, the USA were the first to
land men on the Moon and return them safely to Earth. By that time,
probes had been sent to Venus and Mars.
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Manned
Spaceflight
Project Apollo
"I believe this nation should commit itself to
achieving the goal, before this decade is out, of landing a man on
the Moon and returning him safely to Earth. No single space project
in this period will be more impressive to mankind, or more
important in the long-range exploration of space; and none will be
so difficult or expensive to accomplish."
John F. Kennedy
Special Joint Session of Congress
May 25, 1961
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1. Solar System
